Endless Mode is a non-story survival mode in The Flame in the Flood.
Like Campaign Mode, Endless Mode begins with Scout meeting Aesop and Camp Pinewood. Unlike the campaign, there is no radio in the backpack which Aesop brings to her and the journey down The River is entirely self-motivated.
Similar to Campaign Mode, Scout has to survive by ensuring that she takes care of her Survival Needs. However, there is no end point, with the game ending only when Scout has died.
Scout may still meet the river residents from Campaign Mode. However, they have alternate dialogue and do not play the same role in the game. Several will offer trades and Magnolia will offer to heal Scout's afflictions.
Endless Mode has a fixed difficulty level equivalent to Survivalist difficulty in Campaign Mode. Death is permanent, fewer supplies are found in the world, and stats diminish at an increased rate. The items in Aesop's bag will still persist after death (unless this has been toggled off in the Options) and be available in your next Endless Mode game.